The invention relates to an actuator device for actuating a clutch device.
The term xe2x80x9cclutch devicexe2x80x9d in the sense of the present invention means a device by which torque can be transmitted between an input shaft and an output shaft and which can be set into different engagement positions by means of an actuator, whereby the amount of torque that can be transmitted is increased, decreased, or set to zero. The clutch device may be configured with or without power branching and preferably includes a start-up clutch, a friction clutch, a reverse-gear clutch, a laminar disc clutch, a magnet-powder clutch, a converter bypass clutch, or another device of the same general category.
With special preference, the clutch is configured as an electronically controlled clutch device in which the movement between different positions of the clutch can be performed under electronic control. An electronically controlled clutch device has been described by and is available from the assignee of the present invention under the name xe2x80x9cElectronic Clutch Management (ECM)xe2x80x9d. An actuator device as understood in the present context includes in particular an electric motor or a hydraulic device as a drive source. Preferably, the drive source for the actuator device is an electric motor pushing the piston of a hydraulic master cylinder by way of a transfer mechanism. The master-cylinder piston transmits pressure through the hydraulic fluid to a slave cylinder. The slave-cylinder piston is preferably coupled to a pressure plate that is movable relative to a clutch disc. Thus, the electric motor serves to set the amount of force that is acting between the pressure plate and the clutch disc.
An actuator device for a clutch device is known from DE 44 33 825, where an actuator device with an incremental displacement sensor is described. The incremental displacement sensor, which serves to detect changes in the position of the clutch device, is adjusted from time to time by performing a check to verify whether the actuator device is supplied with energy and whether or not the incremental displacement sensor is indicating changes in the position of the clutch device. If the incremental displacement sensor is registering a stationary position while at the same time the actuator device is found to receive energy, this combination of factors is used to identify an end-stop position.
The present invention has the objective of providing an actuator device that is based on a different technical design in comparison to the aforementioned known state of the art.
The actuator device proposed by the present invention serves to actuate a clutch device which has different engagement positions corresponding to different amounts of torque that can be transmitted between a first rotary component and a second rotary component. According to the invention, the actuator device has a position-detecting device that serves to detect at least one of the different engagement positions. This detection is performed independently of a displacement-measuring device that may be provided to measure the engagement position.
The displacement-measuring device which may in certain cases be incorporated in embodiments of the present invention is in particular designed to measure the engagement position or a change in the engagement position of at least one component of the actuator device or the clutch device under a predetermined set of conditions. The displacement-measuring device, which uses in particular a sensor arrangement, is configured either as an absolute or as an incremental measuring device. The displacement-measuring device is preferably based on a concept of detecting a number of markers that are arranged along the displacement path.
The position-detecting device serves to detect at least one engagement position under a predetermined set of conditions. The detection performed by the position-detecting device is independent of characteristic values that are generated by the displacement-measuring device.
In one embodiment of the foregoing concept, the position-detecting device detects or otherwise determines a characteristic value and then performs a comparison between the characteristic value and a predetermined limit. The characteristic value found by the position-detecting device as well as the predetermined limit are independent of a displacement-measuring device that may in some cases exist together with the position-detecting device. The detected or otherwise determined characteristic value preferably represents an electrical quantity, such as a current or voltage, that is supplied to the drive source of the actuator device. Preferably, the characteristic value is representative of the magnitude of the mechanical resistance that the actuator device has to overcome in order to move the clutch. Based on the comparison between the characteristic value and the predetermined limit, the position-detecting device indicates that the actuator device is at a predetermined engagement position or in a predetermined range of engagement positions. In the context of the present invention, the engagement position is indicated either in absolute terms or in relation to another engagement position.
In a further embodiment of the inventive concept, the position-detecting device detects or otherwise determines a characteristic value as well as the time gradient (rate of change) of the characteristic value and then compares the time gradient to at least one predetermined maximum or minimum value for the time gradient. Based on this comparison, the position-detecting device indicates when the actuator device is in at least one predetermined engagement position. The characteristic value or time gradient in this arrangement is independent of a displacement-measuring device that may in some cases also exist, and it is independent of any measurement of the engagement position of the actuator device. In the context of the present invention, an engagement position represents in particular a predetermined position that can be established in absolute terms. According to a particularly preferred embodiment of the invention, an engagement position can also mean a range of engagement positions, i.e., a range of individual engagement positions that can be determined in absolute terms and are either connected with each other or correlated according to a predetermined characteristic.
As a preferred concept, the position detecting device uses a characteristic operating value as a characteristic value for the determination of a predetermined engagement position of the actuator device. A characteristic operating value is generally a variable value that changes during operation of the actuator device or the clutch device and/or during time periods when a vehicle with the actuator device or clutch device is running. With particular preference, the position-detecting device uses exactly one characteristic value and/or exactly one characteristic operating value to determine at least one predetermined engagement position. With preference, the position-detecting device uses a predetermined characteristic operating value of the drive source of the actuator device which, as mentioned above, is preferably configured as an electric motor. The latter is in particular designed to run under voltage control, meaning that the electric motor is operated and the actuator device is driven by applying a predetermined voltage to the electric motor. While the voltage is thus a given quantity, the position-detecting device uses a characteristic value that varies during operation, such as in particular an electric current or an electric impedance or similar physical quantity, to detect a predetermined engagement position. According to a particularly preferred embodiment of the invention, an electric motor that drives the actuator device is designed to run under voltage control, so that the voltage level is given, while the current can vary dependent on the engagement positions of the actuator device; and the position-detecting device uses the value of the current or a time profile of the current to determine at least one predetermined engagement position of the actuator device.
Preferably, the position-detecting device includes a measuring device to measure at least one characteristic operating value for the detection or determination of a predetermined engagement position.
An actuator device according to a preferred embodiment of the invention has a position-detecting device that measures one and only one characteristic operating value. The latter is in particular a characteristic operating value of the actuator device or the clutch device, or of a motor vehicle that is equipped with the inventive actuator device. Based on this one measured operating value, the position-detecting device identifies at least one predetermined engagement position of the actuator device. It is to be emphasized that according to this embodiment of the invention, there are not a plurality of characteristic operating values being measured, but only one single value which, with particular preference, is not based on an actual position measurement nor a displacement measurement of the actuator device. The measured operating value is used to determine at least one predetermined engagement position of the actuator device. This determination can be based on a direct correlation between the operating value and a predetermined engagement position, or the operating value may be subjected to a computation process or to some other method of determination. In particular, the characteristic operating value may be processed by a computer, based on functional relationships.
A characteristic operating value in the sense of the present invention represents in particular an electrical, hydraulic, or mechanical quantity.
Further in preferred embodiments of the invention, the position-detecting device generates at least one signal dependent on the amount of mechanical resistancexe2x80x94i.e., the magnitude of the opposing forcexe2x80x94that the actuator device has to overcome while moving the clutch device from one position to another. Preferably, the actuator device is designed so that the mechanical resistance that opposes a change of the engagement position has a certain magnitude at a predetermined reference position within the range of actuator movement and changes to a different magnitude at the ends of the range and/or in at least one intermediate point of the range and/or substantially over the entire range of actuator movement.
In particular, the variation of the mechanical resistance can be achieved by end stops and/or by an appropriately shaped surface profile interacting with a spring-biased element, or by other suitable design elements. As a preferred solution, an electric drive motor of the actuator device has an output shaft carrying an appropriately shaped surface profile along a circumference. A spring-biased element pushing against the profile generates a variable resistance to the rotary movement of the motor output shaft. Under this same concept, the surface profile may in general be provided on a movable element that is actuated by an electric motor, with a spring-biased element arranged to push against the profile curve, so that as a result, the movement of the mechanism is opposed by a mechanical resistance that varies between the different engagement positions.
According to a preferred embodiment of the invention, the position-detecting device for the engagement position is configured so that it retains the ability to identify at least one engagement position of the actuator device even in the case of a total breakdown of a displacement-measuring device (in cases where the actuator device is equipped with a displacement-measuring device). It is preferred if the position-detecting device is designed to detect at least one predetermined engagement position regardless of whether the actuator arrangement includes a displacement-measuring device and regardless of whether the latter indicates any measurement signal at all or whether it fails to indicate a change when the actuator device moves. With special preference, the position-detecting device is designed so that it will detect at least two and preferably three different engagement positions even in case of a total failure of a displacement-measuring device, in cases where the latter is provided.
With particular preference, the position-detecting device is designed to perform a redundant detection of at least one predetermined engagement position, where that position is also being measured by a displacement-measuring device, and where the position-detecting device operates independently of the displacement-measuring device.
In certain preferred embodiments of the invention, the actuator device includes a displacement-measuring device to identify a current engagement position of the actuator device. The measurement values for the engagement positions are used in particular for the control of the actuator device. Under a preferred concept, the actuator device has a drive source that includes a voltage-controlled electric motor. The voltage supplied to the motor is controlled as a function of the engagement position as determined by the displacement-measuring device. A position-detecting device, which is also part of the actuator, will under certain conditions generate a command signal to initiate a shut-down of the displacement-measuring device, or to withhold the measurement value of the displacement-measuring device from the control of the electric motor, or to set the measurement value to a constant default value, that will no longer change during a movement of the actuator device for at least a predetermined length of time. When or after the displacement-measuring device has been switched off, the position-detecting device will cause the drive source or, more specifically, the electric motor to be supplied with a predetermined amount of energy for a predetermined length of time. This measure is designed to cause the actuator device to move to a predetermined end stop. A sufficient voltage is applied to the motor for a time period that is long enough to ensure that the actuator device will reach the end stop regardless of the current position from which the actuator device has to be moved to the predetermined end position. Specifically, the voltage and the time period are set so that the actuator device will reach the predetermined end stop even from a current position at the farthest possible distance.
At the end of the predetermined time period, or after the drive source has been supplied with a predetermined amount of energy in the direction towards the end stop, or in general after the measure to ensure the movement to the end stop has been completed, the supply of energy to the drive source is shut off, and the arrival at an end-stop position is registered. The sequence of steps initiated by the command signal is used in particular as an emergency procedure which is started after it has been found that the displacement-measuring device is generating incorrect values or has ceased to operate, or under other conditions, such as an insufficient level of confidence in the values supplied by the displacement-measuring device. With particular preference, the process initiated by the command signal is started in accordance with a predetermined characteristic, e.g., at predetermined time intervals or in predetermined states of the actuator device. With special preference, the clutch device under predetermined conditions is moved into full disengagement or full engagement, with the disengagement or engagement being started by the command signal. Preferably, the disengagement and engagement are directed by a control unit in a manner compatible with the current operating situation of the vehicle. In particular, the command signal may be issued for example when the motor vehicle is standing still or when the brakes are applied.
According to a particularly preferred embodiment of the invention, the displacement-measuring device is reactivated after the arrival at the end stop has been registered. When or after the displacement-measuring device is activated, it is set to a predetermined value, or it is kept at the value that was indicated by the displacement-measuring device at the time it was shut off, or it is kept at the value to which it was set at the shut-off. Subsequent to its reactivation, the displacement-measuring device resumes the indication of displacement values relative to the reference value that was set on reactivation.
Preferably, the position-detecting device is designed so that it can detect at least three different engagement positions of the actuator device. According to a particularly preferred embodiment of the invention, the position-detecting device under certain conditions determines at least one engagement position that is arranged between the terminal positions delimiting the displacement range of the clutch device or the actuating device.
Preferably, the position-detecting device is designed so that it identifies a predetermined engagement position of the actuator device under predetermined conditions based on a motion-related characteristic value that depends on at least one characteristic operating value measured by the position-detecting device. In particular, the measured characteristic operating value is not a position value of an engagement position. It is further preferred to determine the rate of change (also referred to as time gradient) of a motion-related characteristic value. Preferably, the time gradient of a motion-related characteristic value, or the motion-related value itself, is used to identify the position that the actuator device is currently set at.
As a particularly preferred concept, the motion-related characteristic value is dependent on a characteristic electrical value of the actuator device. In particular, the characteristic electrical value may be an impedance or an electric current or voltage of the actuator motor.
With preference, the motion-related characteristic value is dependent on the sense of direction in which the actuator device, the drive source, or the electric motor is working.
Preferably, the motion-related characteristic value or its time gradient is monitored. The occurrence of a local extreme, i.e., a peak or dip in the profile of the motion-related characteristic value indicates that a certain engagement position of the actuator device has been reached. Preferably, the occurrence of an absolute extreme is used to indicate that the actuator device has been set to a predetermined engagement position. With preference, the position-detecting device uses at least a second characteristic value, particularly a second characteristic operating value or a value that is a function of the motion-related characteristic value, in order to differentiate and indicate engagement positions with greater precision, reliability, or in more detail. The second characteristic value is in particular a quantity that depends on the amount of energy or the peak amount of energy supplied to the drive source of the actuator device under certain conditions, particularly in start-up phases. With particular preference, the second characteristic value is selected as the maximum value that can occur during a predetermined time interval in a predetermined function that depends on a time integral of the motion-related characteristic value. The predetermined time interval is in particular a time interval of predetermined length, which begins when the drive source of the actuator device, i.e., the electric motor, is started.
According to a preferred embodiment of the invention, a motion-related characteristic value is determined and then compared to a predetermined limit value. The result of this comparison is used under predetermined conditions to determine an engagement position of the actuator device. In the present context, the term xe2x80x9cengagement positionxe2x80x9d may also mean a range of engagement positions. The limit value depends in particular on the second characteristic value, i.e., the characteristic value that is a function of the motion-related characteristic value.
In the sense of the present invention, a motion-related characteristic value is in particular a quantity that depends on at least one of the characteristic values that have an influence on the movement of the actuator device. In particular, the motion-related characteristic value is a quantity that depends on the mechanical resistance, i.e., the force that opposes the movement of the actuator device.
According to a particularly preferred embodiment of the invention, the motion-related characteristic value at the start-up of the drive source of the actuator device (more specifically, the electric motor) is larger than the limit value that applies to the motion-related characteristic value. The limit value, in turn, is larger than the second characteristic value.
With preference, both the motion-related characteristic value and the second characteristic value are larger than the limit value for the motion-related characteristic value in operating situations where the actuator device is at an end stop. According to a particularly preferred embodiment of the invention, the actuator device has a displacement-measuring device measuring an actual position. The latter is compared to a predetermined reference position if the actuator device has been found to have arrived at a predetermined engagement position or a limit stop position. The reference position is correlated with the limit stop position or with the engagement position in accordance with a predetermined characteristic. If necessary, the reference position and the actual position are reconciled with each other at this point.
The drive source in preferred embodiments of the invention is designed to drive the actuator device in either sense of direction.
In certain embodiments where the drive source is an electric motor, the drive energy or a characteristic value that determines the drive energy, such as a voltage or the time interval during which the voltage is applied without changing the sense of direction, is limited to a predetermined total amount of energy or to a predetermined voltage, or a predetermined duration, or a similar limit criterion. After the drive source has been supplied with a specific total or cumulative amount of energy without changing the sense of direction, the drive source is switched off at least temporarily. With particular preference, in determining the cumulative amount of energy, only those time segments of the energy flow are counted which exceed a predetermined energy level. In particular, any segments in the energy flow are not counted which are too small to overcome the system-inherent friction of the actuator device and to cause a movement of the actuator device.
According to a particularly preferred embodiment of the invention, a condition where the aforementioned specific amount of total energy has been supplied to the drive source of the actuator device without a change in the sense of direction is interpreted as a completed move to an end-stop position.
Under a preferred concept of the invention, an actuator device equipped with an electric motor as a drive source has a means of determining a confidence level that allows a quantitative or qualitative determination of the probability that the engagement positions of the clutch device were determined correctly.
Dependent on the aforementioned confidence level, a limit for the total energy to be supplied to the electric motor is set at a predetermined value.
The scope of the invention further includes any clutch device that is equipped with an actuator device conforming to one of embodiments described herein.
Also included under the scope of the present invention is any method of operating an actuator device in accordance with the concepts implied in the embodiments discussed herein.
As a linguistic formality, where the names of features are connected by the word xe2x80x9corxe2x80x9d, this should be understood in the broadest sense, i.e., either as a logic type of or (one or the other or both) or an exclusive or (one or the other but not both), whichever fits the context.
The terms xe2x80x9ccontrolxe2x80x9d and xe2x80x9cregulationxe2x80x9d and their derivatives are used herein with a broad range of meanings encompassing closed-loop as well as open-loop control of devices, functions and processes, including in particular the DIN (Deutsche Industrie-Norm) definitions for regulation and/or control).
The novel features that are considered as characteristic of the invention are set forth in particular in the appended claims. The improved apparatus itself, however, both as to its construction and its mode of operation, together with additional features and advantages thereof, will be best understood upon perusal of the following detailed description of certain presently preferred specific embodiments with reference to the accompanying drawing.